1. Field of the Invention
The present invention relates to an underground tank having a leak detection mechanism, and particularly relates to an underground tank having a mechanism for detecting the leak of a contained substance such as gasoline.
2. Description of the Prior Art
Since a conventional underground tank for oil such as gasoline at an oil handling facility such as a filling station is made of steel in accordance with the Fire Services Act, the underground tank is likely to corrode and the tank portion right under an oil pouring port is likely to be holed (eroded).
Even if the outside surface of the conventional underground tank is coated with a bituminous substance such as coal tar for rust prevention, the coating layer of the bituminous substance is dissolved by oil permeating through the ground from the surface thereof, so that the outside surface of the tank is likely to corrode.
It is not easy to find out whether the underground tank is holed or not.